This invention pertains to an electrolytic cell and more in particular to an improved means to reduce the inter-electrode distance in an electrolytic cell.
Gaseous chlorine has long been produced from an aqueous solution or slurry containing an alkali metal chloride, such as sodium chloride, in an electrolytic cell having an anode positioned within an anode compartment and a cathode in a cathode compartment spaced apart from the anode compartment by an ion and liquid permeable diaphragm. In recent years, cation exchange membranes have been developed which permit the passage of positively charged ions from the anode compartment to the cathode compartment without allowing substantial quantities of negatively charged ions and water to pass from the cathode compartment to the anode compartment. In both the electrolytic diaphragm and membrane type cells chlorine is released at the anode and alkali metal hydroxide, such as sodium hydroxide, is formed in the cathode compartment.
It has become apparent that the use of the cation exchange membrane type cells may be preferable to the diaphragm cell in instances where a higher purity, for example a lower sodium chloride content, sodium hydroxide product is desired. It has also been found to be more convenient to fabricate the membrane type electrolytic cells from relatively flat or planar sheets of ion exchange membrane rather than to interweave the membrane between the anode and cathode within the older diaphragm cells, which had anodes interposed between cathodes in a finger-like arrangement.
The newer, so-called flat-plate bipolar electrolytic cells using a planar piece of ion exchange membrane to separate the anolyte from the catholyte compartments are similar to the diaphragm cells insofar as there is a common attempt to minimize the distance between the anode and the cathode. A minimum electrode spacing is desired so that the electrical resistance between electrodes will be reduced and the cell efficiency improved.
There have been several attempts to reduce the inter-electrode spacing in the flat-plate electrolytic cell. It is, however, desired to provide a relatively uncomplicated, readily useable means to retain the electrodes in an ion exchange membrane cell in close proximity to each other.